The role of location determination in wireless mobile communication systems is gaining importance, with services such as navigation, search, proximity, safety & security all depending on it. In certain types of wireless location systems, the location of a mobile device is measured with respect to one or more fixed transmitter sites whose locations are known. The location determination algorithms in such systems may also take into account other parameters where available, describing the configuration of the transmitters including antenna parameters, orientation and transmit power levels.
In certain cases the information on the configuration of the transmitters may already be held by the service provider and therefore available for use in the location determination system. For example the service provider may be a cellular network operator. In this case, details on the configuration of the radio access network is typically maintained by a radio network planning department within the operator.
In other cases however, a provider of location based mobile services may not have certain information concerning the configuration of the access networks through which users access a service. In order to obtain location information for use in the offered services, certain providers of such mobile location based services have developed systems and methods in attempts to obtain the wireless transmitter configuration information using dedicated survey measurements. Other service providers have developed systems and methods for collecting wireless transmitter characteristics in an opportunistic fashion as subscribers utilize the service. For example, subscribers having a GPS handset and accessing the service may contribute one or more measurements of a transmitter accompanied by a GPS position fix. In certain cases both survey measurements as well as opportunistic measurements may be combined.
Notwithstanding these methods of obtaining the transmitter configuration information, several limitations remain with the provision of mobile location based services where information on the configuration of the radio network is sought. One limitation is due to changes in the configuration of such networks from time to time. Existing systems are commonly slow to account for changes in the configuration of the radio network. For example it has been observed with one publicly available mobile mapping service that a change in the configuration of some UMTS cells in a region of London resulted in a substantial loss of coverage for a period lasting at least 12 days. This was despite repeated requests from handsets with a GPS activated, in an attempt to “seed” the cell database. For users of such systems it may be useful to have continuous service and therefore desirable that the location determination system can detect and respond to changes in the wireless network promptly, thereby maintaining the quality of the location service. One reason that existing systems cannot respond to changes in the wireless network configuration promptly is that the configuration information is mainly collected through costly and time consuming manual surveys or “war driving” of the networks. Such data may in some cases also be augmented with other data collected opportunistically when for instance a user requests a map on a cellular device while having an inbuilt GPS enabled. In this case, the mapping application may also collect information on the current serving cell and report this along with the current GPS coordinates to a server. With either or both of these strategies for data collection in use, there remains the issue that changes in a particular location may take a considerable time to recover, either by waiting until the next drive test in that location or by waiting for a cooperative user to enable a GPS on their terminal and initiate one or measurements from the affected region.
A further limitation of existing systems is that it is commonly necessary with such systems to repeat network surveys periodically to refresh the network configuration database to reflect changes since the previous survey which have not been detected through the opportunistic collection of measurements. From a commercial perspective this can represent a significant burden to providers of services based on such a database.
The limitations described in the previous paragraphs and other limitations can be overcome using systems, methods and/or devices which can more rapidly and efficiently collect wireless network configuration information and can be operated to respond to changes in the network configuration more rapidly than existing systems, methods and/or devices thereby enhancing the accuracy and coverage of the wireless configuration database and preserving a better level of service for users of location systems utilizing the database. For the foregoing reasons, there is a need for systems, methods and devices which can collect the measurements needed to characterize the transmitters in a wireless network, more efficiently and more rapidly. There is also a need for systems, methods and/or devices that are responsive to the current quality or coverage of the wireless network transmitter database and which can accelerate the collection rate at times when there is a greater need for measurement information and furthermore can focus the measurements on regions of the network where the database coverage is less accurate or complete. There is also a need for systems, methods and devices that are scalable as the services supported by such systems may be offered across many networks in many markets to many millions of subscribers
For providers of location based services using an independently acquired database of wireless transmitter characteristics there is another challenge with existing systems, namely that all of or at least a substantial proportion of the geographical area to be served must be covered by the transmitter database before a service can be successfully offered. With existing systems, either the service provider must invest in a costly surveying exercise before launching the service or else must rely on opportunistic measurements from early users who are willing to tolerate poor service in some instances or else some combination of both to achieve a sufficient level of coverage. There is therefore further need for systems, methods and devices which can more efficiently collect the required transmitter information and can accelerate the acquisition process in the early stages of a service when user populations are smaller and the coverage of the transmitter database may be incomplete.